Single Sided, Dual Plunger Pump

ABSTRACT

A single sided, dual plunger pump is disclosed for use pumping difficult working fluids, including fluids with high particulate content. Each plunger operates in the opposite state as the other, such that when one plunger is filling with fluid, the other is discharging, and so forth. This creates discharge flow that is much more stable than a pump using only a single plunger, without requiring two individual pumps to be connected together.

FIELD

This invention relates to the field of pumps and more particularly to a device for nearly continuous pumping of highly viscous or particulate laden fluids.

BACKGROUND

Many pumps are inappropriate for pumping highly viscous fluids, or fluids that have a high particulate content. There are existing pumps that can handle such difficult working fluids but do so with drawbacks, namely limited pressure increase or intermittent fluid flow.

Prior art pumps exist that can pump difficult fluids. For abrasive fluids, a diaphragm or membrane pump is often recommended. Such pumps operate by sharing a flexible wall between a fluid chamber containing a working fluid and a pressure chamber, the pressure chamber alternately pressured and depressurized. A check valve on the inlet and another on the outlet of the working fluid chamber prevents backflow. When the pressure chamber is depressurized, working fluid is drawn into the fluid chamber. When the pressure chamber is pressurized, the working fluid is pushed out of the fluid chamber. Alternating these two steps pumps fluid. But there are multiple drawbacks to a diaphragm pump. In a diaphragm pump, the discharge pressure of the working fluid cannot exceed that of the pressure source supplying the pressure chamber, commonly air. This is because the membrane area acted upon by the air pressure is the same membrane area acting upon the working fluid. Also, due to the intermittent nature of the pumping, the fluid is discharged in pulses.

A plunger pump addresses some of the shortcomings of a diaphragm pump, specifically the limitation of low pressure differential. But similar to a diaphragm pump and a piston pump, the pumping of a plunger pump is intermittent, causing surging discharge pressure and flow.

U.S. Pat. No. 4,029,442 to Schlosser discloses a high pressure plunger pump for use pumping heavy, highly viscous, and abrasive materials. The '442 patent discloses the use of an elastomeric ring to form a seal between the wall that separates the high and low pressure chambers, and the outer wall of the piston. This elastomeric ring functions as a pressure barrier, preventing pressurized fluid from leaking backwards across the plunger. More importantly, the seal also acts as a wiper. The wiper cleans material from the plunger wall during each stroke, preventing aggregate suspended within the material from scratching the surface of the plunger. But the Schlosser device does not disclose the use of multiple plungers within a single enclosure, alternating between intake and discharge.

What is needed is a system that will allow nearly continuous pumping of difficult working fluids, with the potential for significant pressure differentials between the inlet and outlet.

SUMMARY

Described within is a pump apparatus comprising a housing, the housing having a proximal end, the proximal end having a penetration, a proximal low pressure chamber, a proximal high pressure chamber, a distal end, a distal low pressure chamber, and a distal high pressure chamber, a shaft, the shaft located within the penetration and extending through a portion of the housing, a proximal plunger, the proximal plunger affixed to the shaft, a distal plunger, the distal plunger affixed to the shaft, a proximal chamber seal, the proximal chamber seal having an inner diameter and an outer diameter, the proximal chamber seal located at an interface of the proximal low pressure chamber and the proximal high pressure chamber, a distal chamber seal, the distal chamber seal having an inner diameter and an outer diameter, the distal chamber seal located at an interface of the distal low pressure chamber and the distal high pressure chamber, whereas when the proximal plunger moves toward the proximal high pressure chamber, and away from the proximal low pressure chamber, the distal plunger moves away from the distal high pressure chamber, and toward the distal low pressure chamber.

Further disclosed is a pump apparatus comprising, a housing, the housing having a proximal end, the proximal end having a penetration, a proximal low pressure chamber, a proximal high pressure chamber, a distal end, a distal low pressure chamber, and a distal high pressure chamber, a shaft, the shaft located within the penetration and extending through a portion of the housing, the shaft comprised of one or more pieces, a proximal plunger, the proximal plunger integral to at least one portion of the shaft, a distal plunger, the distal plunger integral to at least one piece of the shaft, a proximal chamber seal, the proximal chamber seal interposed between the proximal low pressure chamber and the proximal high pressure chamber, a distal chamber seal, the distal chamber seal interposed between the distal low pressure chamber and the distal high pressure chamber, whereas while the proximal plunger moves into the proximal high pressure chamber, and out of the proximal low pressure chamber, the distal plunger moves out of the distal high pressure chamber, and into the distal low pressure chamber.

Finally, disclosed is a pump apparatus comprising, a housing, the housing having a proximal end, the proximal end having a penetration, a proximal low pressure chamber, a proximal high pressure chamber, a distal end, a distal low pressure chamber, and a distal high pressure chamber, a cylindrical shaft, the cylindrical shaft located within the penetration and extending through a portion of the housing, the cylindrical shaft comprised of one or more pieces, a proximal plunger, the proximal plunger integral to at least one portion of the cylindrical shaft, a distal plunger, the distal plunger integral to at least one piece of the cylindrical shaft, a proximal chamber seal, the proximal chamber seal interposed between the proximal low pressure chamber and the proximal high pressure chamber, a distal chamber seal, the distal chamber seal interposed between the distal low pressure chamber and the distal high pressure chamber, wherein the proximal low pressure chamber is near the proximal end of the housing, the proximal high pressure chamber is between a center of the housing and the proximal low pressure chamber, the distal high pressure chamber is between the center of the housing and the distal low pressure chamber, and the distal low pressure chamber is near the distal end of the housing; and as the proximal plunger moves into the proximal high pressure chamber, and out of the proximal low pressure chamber, the distal plunger moves out of the distal high pressure chamber, and into the distal low pressure chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be best understood by those having ordinary skill in the art by reference to the following detailed description when considered in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a plan view of a single sided, dual plunger pump.

FIG. 2 illustrates a cutaway view of the single sided, dual plunger pump.

FIG. 3 illustrates a side plan view of the single sided, dual plunger pump.

FIG. 4 illustrates another cutaway view of the single sided, dual plunger pump.

FIG. 5 illustrates a close-up cutaway view of the shaft seals of the single sided, dual plunger pump.

FIG. 6 illustrates a close-up cutaway view of the second cylinder and associated components of the single sided, dual plunger pump.

DETAILED DESCRIPTION

Reference will now be made in detail to the presently preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Throughout the following detailed description, the same reference numerals refer to the same elements in all figures.

Referring to FIGS. 1 and 2, the frontal view of a first embodiment of the dual piston, single sided plunger pump is shown. The pump is shown in a vertical orientation, but is used in any orientation. The driver attachment point 2 connects to a pump driver (not shown). This portion of the pump will be referred to as the proximal portion, the driver attachment point 2 used as a point of reference. The pump driver is most frequently a linear air motor (pneumatic motor) powered by a source of compressed air, but any source of oscillating force is anticipated to provide the power necessary for operation. A penetration 3 is present at the top of the pump housing 100 to allow the shaft components 126/124/123/10/60 to connect to an air motor (not shown).

The optional surge chambers 6/8 are shown. This embodiment includes surge chambers 6/8 to smooth out pressure fluctuations that result from varying inlet conditions. In other embodiments the surge chambers are not present.

Moving to the internal parts of the pump, four chambers are shown. Each of the two plungers 10/60 has a low pressure chamber 12/62 and a high pressure chamber 14/64. The proximal plunger 10, or plunger closest to the driver attachment point 2, oscillates between a proximal low pressure chamber 12 and a proximal high pressure chamber 14. The distal plunger 60, or plunger furthest from the driver attachment point 2, oscillates between a distal low pressure chamber 62 and a distal high pressure chamber 64.

The operation of the dual plunger pump 1 will be described. When there exists a fixed volume of space filled with fluid, and an additional volume is introduced into the space, the fluid pressure increases. In the dual plunger pump 1, the high pressure chambers 14/64 have a fixed volume. As the plunger 10/60 moves into the high pressure chamber 14/64, contacting the seal 40/90, the space available to be occupied by the fluid decreases, pressure increases, and fluid exits, passing through the check valve 18/68. This example contains discharge check valves 18/68, but in other embodiments there are no discharge check valves 18/68. The example shown uses ball check valves, but the use of other types of check valves is anticipated, including swing check valves, tilting disc check valves, dual plate check valves, and others as are known in the art.

The manner in which the dual plunger pump 1 operates allows the seal 40/90 to clean the plunger 10/60 during operation. What follows is a description of a single cycle of one plunger, starting with the plunger 10/60 within the low pressure chamber 12/62.

When the plunger 10/60 is starting its stroke, it is within the low pressure chamber 12/62. The walls of the plunger 10/60 are not in contact with the seal 40/90. As the plunger 10/60 in the dual plunger pump 1 moves from the low pressure chamber 12/62 to the high pressure chamber 14/64, the wall of the plunger 10/60 contacts the seal 40/90. Each plunger 10/60 has a seal 40/90 positioned between the plunger 10/60 wall and the inner portion of the pump housing 100. As the wall of the plunger 10/60 moves through the seal 40/90, the seal 40/90 wipes any debris from the plunger 10/60 wall, returning it to the working fluid. The plunger 10/60 then returns to the low pressure chamber 12/62, and the cycle begins again. As the plunger 10/60 returns to the low pressure chamber 12/62, a vacuum is created in the high pressure chamber 14/64. This vacuum draws new working fluid into the high pressure chamber 14/64, preparing it for the next cycle. The plunger 10/60 is wiped during each stroke to prevent abrasive material from accumulating on the plunger 10/60 wall, instead pushing the abrasive material back into suspension, to be pumped through on the next stroke.

The surge chambers 6/8, when installed, work to buffer/decrease pressure fluctuations in the low pressure chambers 12/62. When the plunger 10/60 is returning to the low pressure chamber 12/62, working fluid must be displaced to make room for the volume of the plunger 10/60. The working fluid will either move out one of the inlets 101/102, or into the surge chambers 6/8. Either way, when the plunger 10/60 moves out of the low pressure chamber 12/62, the working fluid will be pulled into the low pressure chamber 12/62 to fill the space left by the plunger 10/60. Whether or not surge chambers are appropriate for use depends on the service of the pump and the type/properties of working fluid.

The pressurized fluid is discharged past valves 18/68 and through the discharge 106. Plugs 120/121 are present to allow the check valves 18/68 to be cleaned out.

Referring now to FIGS. 3 and 4, a side view of the pump is shown. The pump has multiple input locations that are selected based on service and orientation. The use of dual plungers created a filling problem, solved in the dual plunger pump 1 by the use of specific inlets for certain orientations. In FIGS. 3 & 4, an alternative inlet 102 is shown. In this example, the pump is used in a vertical orientation. In other embodiments the vertical inlet 101 is used. In still other embodiments, inlets are present in other locations, such as the distal portion of the housing.

When the pump is in a horizontal orientation, filling through the alternate inlet 102 provides fluid to both the low pressure chambers 12/62 equally. In contrast, when the pump is orientated vertically as shown in FIG. 4, using the alternative inlet 102 fills distal low pressure chamber 62 first, but traps air within the dual plunger pump 1, preventing proximal low pressure chamber 12 from filling. Therefore, a vertical inlet 101 is provided for vertical orientations. To use the vertical inlet 101, the alternative inlet 102 is plugged/blocked and the pump is filled through vertical inlet 101. When in a vertical orientation, fluid is introduced through the vertical input location 101, passing through the proximal low pressure chamber 12, into the inlet jumper 104, and finally into the distal low pressure chamber 62. When the pump is then started, both low pressure chambers 12/62 are filled with fluid and pumping of the fluid starts immediately, rather than having only one low pressure chamber 12/62 pumping fluid and the other low pressure chamber 12/62 only partially full. Starting the dual plunger pump 1 with both chambers full minimizes the presence of air in the discharge.

Referring now to FIG. 5, a larger view of the center seals is shown. There are two primary sets of seals 30/80/32/82. One set of seals, the fluid seals 30/80 keeps the pressure from the high pressure chambers 14/64 from leaking into the area surrounding the bearing 110, or from one chamber 14/64 to the other chamber 14/64. Supporting the shaft center portion 123 is a bearing 110. In this embodiment the bearing 110 is a plain bearing (friction bearing) lubricated with oil. Oil is provided by the oil reservoir 112. The second set of seals is the oil seals 32/82 that prevent the oil from leaving the area surrounding the bearing 110, thereby reducing oil use and contamination of the working fluid.

In this example the seals 30/32/80/82 are U-shaped, with an internal spring, known as spring energized seals. The internal spring preloads the seals 30/32/80/82, providing some level of sealing even in the absence of pressure. The open portion of the U shape of the seals 30/32/80/82 faces toward the high pressure side of the seal 30/32/80/82. This allows the fluid pressure to press against the inside of the seals 30/32/80/82, forcing the outside of the seals 30/32/80/82 against the adjacent surfaces, creating a tight seal that becomes even tighter as pressure increases. In other embodiments the seals 30/32/80/82 are dynamic o-rings, o-ring energized seals, or o-ring seals.

The bearings are held in cartridges 36/86, which are sealed to the pump housing by seals 34/84. In this embodiment the seals 34/84 are static o-rings, but in other embodiments other types of seal are employed as known in the art.

Dual plunger pump 1 is well suited for use with viscous fluids, such as epoxy resins. The Dual plunger pump 1 is also well suited for use with coatings that cure or have fillers that collect in crevices, making pump service and repair difficult. The use of such materials can lead to difficulties when the dual plunger pump 1 needs cleaning, seal replacement, or general maintenance. The cartridges 36/86 lay in the bottom of their respective high pressure chambers 14/64 and are sometimes difficult to remove. Alternate embodiments of the dual plunger pump 1 include a break in the pump housing 100 near the cartridges 36/86 to facilitate removal of cartridge 36/86. In other embodiments, the portion of the housing 100 between the cartridges 36/86 is removable, allowing the cartridges 36/86 to be pushed out of the pump housing 100, such as through use of a wooden block and a hammer.

Referring now to FIG. 6, a close up of a single plunger 60 with its associated components is shown. The seal 90 is shown, next to the guide 92. The plunger 60 is only supported on one end and the guide 92 serves as a centering device, helping the plunger 60 to meet the seal 90 while centered. The beveled sides of the guide 92 allow the plunger 60 to be pushed back toward center as part of the discharge stroke. In some embodiments, the guide 92 is missing, with the seal 90 being able to compensate for an off-center plunger 60 by either having sufficient stiffness to center the plunger 60 or sufficient flexibility to seal despite the plunger 60 being off-center.

Referring now to FIGS. 1-6, the pump overall will be described. The dual plunger pump 1 provides almost a continuous flow of fluid by having two plungers 10/60 with associated low and high pressure chambers 12/62/14/64. The arrangement of plungers 10/60 in the dual plunger pump 1 results in a need for additional seals 30/32/34/80/82/84. The penetration 3 into the proximal low pressure chamber 12 is sealed with a bellows 130. The center of the pump separates the two high pressure chambers 14/64 using cartridges 36/86 with seals 30/32/34/80/82/84, as discussed above.

The bellows 130 is a pressure barrier between the outside of the pump, assumed to be at atmospheric pressure (though there is no reason the pump could not operate surrounded by a higher or lower pressure), and the pressure within the low pressure chambers 12/62 varying, often below atmospheric pressure (i.e., a slight vacuum). When a transfer pump is used (such as to pull material out of a barrel) the pressure within the low pressure chambers 12/62 is greater, though generally no higher than 15 psig. The proximal end of the bellows 130 is sealed by compression between the upper sealing ring 5 and the pump housing 100. The distal end of the bellows 130 is sealed by compression between the proximal shaft section 126 and proximal plunger 10. The bellows 130 is sized to avoid rubbing against the proximal shaft section 126 or the sides of penetration 3 through pump housing 100. The upper sealing ring 5 attaches to the pump housing 100 in numerous possible ways, including threading into the pump housing 100, or by having a flanged connection and bolted to the pump housing 100, or any other means of attachment as known in the art.

Because the center of the shaft requires support to remain coaxial with the low and high pressure chambers 12/62/14/64, a bearing 110 is included, with associated oil reservoir 112 and seals 32/82. As discussed, the oil reservoir 112 provides oil to the bearing area, keeping the bearing 110 lubricated, as well as the shaft center portion 123. The oiled portion extends away from the bearing in both directions, with oil being wiped from the shaft center portion 123 by the seals 32/82.

The dual plunger pump 1 has two modes of operation. In one mode both chambers 12/62 are fed the same fluid. In the other mode each chamber 12/62 is fed a different fluid. When both chambers are fed the same fluid, the output flow is substantially continuous, only ebbing when the shaft 123/124/126 changes direction.

In the continuous discharge mode, the dual plunger pump 1 makes nearly continuous discharge possible by using two plungers, and opposing their strokes. When the proximal plunger 10 is filling with fluid, the distal plunger 60 is discharging fluid. The directions then reverse, with the distal plunger 60 filling with fluid and the proximal plunger 10 discharging fluid. There is a slight lag between the two motions as directions change and the plunger 10/60 about to pump approaches its seal 40/90. But with the exception of this lag, this arrangement creates a nearly continuous discharge.

When the dual plunger pump 1 is used to pump two different fluids, some changes are required from the current example. The inlet jumper 104 is removed and replaced with two individual connections, one to each low pressure chamber 12/62. The discharge manifold 108 is removed and replaced with two individual discharge manifolds, each manifold including its own check valve 18/68 and discharge connection.

While there are many benefits to the dual plunger pump 1, specific benefits are seen in certain applications. In applications where there are two fluids, here called Fluid A and Fluid B, it is useful to use a single dual plunger pump 1 to pump Fluid A, and attach small pump to the opposite side of the driver. The small pump then pumps some percentage of Fluid B, resulting in the proper mix of the two fluids. Or for other applications where the mix ratio of Fluid A and Fluid B is 1:1, a dual plunger pump 1 is installed on each side of a driver, allowing one driver to power two dual plunger pumps.

Referring now to FIGS. 1-6, assembly of the dual plunger pump 1 will be described. The moving portion of the dual plunger pump 1 consists of the air motor attachment point 2, proximal shaft section 126, proximal plunger 10, threaded rod 124, shaft center portion 123, and distal plunger 60. In this embodiment the distal plunger 60 is held to the shaft center portion 123 by a threaded bolt 122. Proximal shaft section 126 penetrates the proximal plunger 10, compressing the proximal plunger 10 between proximal shaft section 126 and shaft center portion 123. In some embodiments the shafts 126/124/123 are threaded into one another, and the plungers 10/60. In other embodiments they are press fit (interference fit), or attached using any other means of attachment as known in the art. In still other embodiments, the plungers 10/60 and shafts 126/124/123 are machined as a single piece.

The dual plunger pump 1 is shown with the low pressure chambers 12/62 near the ends, and the high pressure chambers 14/34 near the center. This is not a requirement; rather, the dual plunger pump 1 functions with the low pressure chambers 12/62 near the center and the high pressure chambers 14/64 near the ends. In this modified design, many associated parts are be relocated, as known in the art, as needed to accommodate the new locations. Notwithstanding, the modified dual plunger pump 1 operates as described above.

Equivalent elements can be substituted for the ones set forth above such that they perform in substantially the same manner in substantially the same way for achieving substantially the same result.

It is believed that the system and method as described and many of its attendant advantages will be understood by the foregoing description. It is also believed that it will be apparent that various changes may be made in the form, construction and arrangement of the components thereof without departing from the scope and spirit of the invention or without sacrificing all of its material advantages. The form herein before described being merely exemplary and explanatory embodiment thereof. It is the intention of the following claims to encompass and include such changes. 

What is claimed is:
 1. A pump apparatus comprising: a housing, the housing having a proximal end, the proximal end having a penetration, a proximal low pressure chamber, a proximal high pressure chamber, a distal end, a distal low pressure chamber, and a distal high pressure chamber ; a shaft, the shaft located within the penetration and extending through a portion of the housing; a proximal plunger, the proximal plunger affixed to the shaft; a distal plunger, the distal plunger affixed to the shaft; a proximal chamber seal, the proximal chamber seal having an inner diameter and an outer diameter, the proximal chamber seal located at an interface of the proximal low pressure chamber and the proximal high pressure chamber; a distal chamber seal, the distal chamber seal having an inner diameter and an outer diameter, the distal chamber seal located at an interface of the distal low pressure chamber and the distal high pressure chamber; whereas when the proximal plunger moves toward the proximal high pressure chamber, and away from the proximal low pressure chamber, the distal plunger moves away from the distal high pressure chamber, and toward the distal low pressure chamber.
 2. The pump apparatus of claim 1, further comprising; a bearing, the bearing located substantially at a center of the shaft, the bearing supporting the shaft to allow movement of the shaft but preventing contact with the housing.
 3. The pump apparatus of claim 2, further comprising; an oil reservoir, the oil reservoir connected by a channel to the bearing, providing oil to lubricate an interface between the shaft and the bearing.
 4. The pump apparatus of claim 3, further comprising: a proximal fluid seal, the proximal fluid seal surrounding the shaft, located between the proximal plunger and a center of the housing, creating a seal between the shaft and the housing; a distal fluid seal, the distal fluid seal surrounding the shaft, located between the distal plunger and the center of the housing, creating a seal between the shaft and the housing;
 5. The pump apparatus of claim 4, further comprising: a proximal oil seal, the proximal oil seal surrounding the shaft, located between the proximal fluid seal and the bearing, creating a seal between the shaft and the housing; a distal oil seal, the distal oil seal surrounding the shaft, located between the distal fluid seal and the bearing, creating a seal between the shaft and the housing.
 6. The pump apparatus of claim 1, further comprising: a proximal plunger guide, the proximal plunger guide adjacent to the proximal chamber seal, guiding the proximal plunger as it moves between the low pressure proximal chamber and the high pressure proximal chamber a distal plunger guide, the distal plunger guide adjacent to the distal chamber seal, guiding the distal plunger as it moves between the low pressure distal chamber and the high pressure distal chamber.
 7. The pump apparatus of claim 1, further comprising: one or more intake check valves, the one or more intake check valves located on an inlet to the proximal/distal low pressure chambers, the one or more intake check valves allowing flow into the low pressure chambers, but not out of the low pressure chambers.
 8. The pump apparatus of claim 1, further comprising: one or more discharge check valves, the one or more discharge check valves located on an outlet of the proximal/distal high pressure chambers, the one or more discharge check valves allowing flow out of the high pressure chambers, but not into the high pressure chambers.
 9. The pump apparatus of claim 1, further comprising: one or more surge chambers, the one or more surge chambers connected to the proximal/distal low pressure chambers.
 10. A pump apparatus comprising: a housing, the housing having a proximal end, the proximal end having a penetration, a proximal low pressure chamber, a proximal high pressure chamber, a distal end, a distal low pressure chamber, and a distal high pressure chamber; a shaft, the shaft located within the penetration and extending through a portion of the housing, the shaft comprised of one or more pieces; a proximal plunger, the proximal plunger integral to at least one portion of the shaft; a distal plunger, the distal plunger integral to at least one piece of the shaft; a proximal chamber seal, the proximal chamber seal interposed between the proximal low pressure chamber and the proximal high pressure chamber; a distal chamber seal, the distal chamber seal interposed between the distal low pressure chamber and the distal high pressure chamber; whereas while the proximal plunger moves into the proximal high pressure chamber, and out of the proximal low pressure chamber, the distal plunger moves out of the distal high pressure chamber, and into the distal low pressure chamber.
 11. The pump apparatus of claim 10, further comprising; a bearing, the bearing located substantially near a center of the housing, the bearing supporting the shaft to allow movement of the shaft but preventing contact with the housing.
 12. The pump apparatus of claim 11, further comprising; an oil reservoir, the oil reservoir connected by a channel to the bearing, providing oil to lubricate an interface between the shaft and the bearing.
 13. The pump apparatus of claim 12, further comprising: a proximal fluid seal, the proximal fluid seal surrounding the shaft, located between the proximal plunger and a center of the housing, creating a seal between the shaft and the housing; a distal fluid seal, the distal fluid seal surrounding the shaft, located between the distal plunger and the center of the housing, creating a seal between the shaft and the housing;
 14. The pump apparatus of claim 13, further comprising: a proximal oil seal, the proximal oil seal surrounding the shaft, located between the proximal fluid seal and the bearing, creating a seal between the shaft and the housing; a distal oil seal, the distal oil seal surrounding the shaft, located between the distal fluid seal and the bearing, creating a seal between the shaft and the housing.
 15. The pump apparatus of claim 10, wherein; the proximal low pressure chamber is near the proximal end of the housing; the proximal high pressure chamber is between a center of the housing and the proximal low pressure chamber; the distal high pressure chamber is between the center of the housing and the distal low pressure chamber; and the distal low pressure chamber is near the distal end of the housing.
 16. The pump apparatus of claim 10, wherein; the proximal high pressure chamber is near the proximal end of the housing; the proximal low pressure chamber is between a center of the housing and the proximal high pressure chamber; the distal low pressure chamber is between the center of the housing and the distal high pressure chamber; and the distal high pressure chamber is near the distal end of the housing.
 17. The pump apparatus of claim 10, further comprising: a proximal intake check valve, the proximal intake check valve located on an inlet to the proximal low pressure chamber, a distal intake check valve, the distal intake check valve located on an inlet to the distal low pressure chamber.
 18. The pump apparatus of claim 11, further comprising: a proximal discharge check valve, the proximal discharge check valve located on a discharge to the proximal high pressure chamber, a distal discharge check valve, the distal discharge check valve located on a discharge to the distal high pressure chamber.
 19. The pump apparatus of claim 12, further comprising: a proximal surge chamber, fluidly connected to the proximal low pressure chamber; a distal surge chamber, fluidly connected to the distal low pressure chamber.
 20. A pump apparatus comprising: a housing, the housing having a proximal end, the proximal end having a penetration, a proximal low pressure chamber, a proximal high pressure chamber, a distal end, a distal low pressure chamber, and a distal high pressure chamber; a cylindrical shaft, the cylindrical shaft located within the penetration and extending through a portion of the housing, the cylindrical shaft comprised of one or more pieces; a proximal plunger, the proximal plunger integral to at least one portion of the cylindrical shaft; a distal plunger, the distal plunger integral to at least one piece of the cylindrical shaft; a proximal chamber seal, the proximal chamber seal interposed between the proximal low pressure chamber and the proximal high pressure chamber; a distal chamber seal, the distal chamber seal interposed between the distal low pressure chamber and the distal high pressure chamber; wherein the proximal low pressure chamber is near the proximal end of the housing, the proximal high pressure chamber is between a center of the housing and the proximal low pressure chamber, the distal high pressure chamber is between the center of the housing and the distal low pressure chamber, and the distal low pressure chamber is near the distal end of the housing; and as the proximal plunger moves into the proximal high pressure chamber, and out of the proximal low pressure chamber, the distal plunger moves out of the distal high pressure chamber, and into the distal low pressure chamber. 